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BQ34Z100-G1: Missing and/or additional info needed for some parameters

BatMan
Expert 1232 points
Part Number: BQ34Z100-G1
Other Parts Discussed in Thread: BQ34Z100

Hi,

I am using the BQ34Z100-G1 device in a scaled configuration with 6 cells in multiple applications.

I am developing an understanding of the relationship of the various parameters to the SOC and SOH calculations

but there are a few parameters that do not have much if any explanation. 

Can you give me any detailed information for the following parameters and how they relate to impedance tracking,  or related reference information?

1) Res Current

2) ResRelax Time

3) Design Resistance

4) Cell Max IR Correct

Secondly, I have found some information that is misleading that you could, perhaps, clear up.

5) Max Res Factor is set to default 50. This is different than the legacy IC BQ27520 default but has no explanation in the BQ34Z100 specification.

6) Likewise, what is Min Res Factor and default?

  • 0
    TI__Mastermind 25955 points
    Hi Tim,

    With your applications, are you scaling for current and/or capacity?

    1) Res Current - determines the min discharge rate that may be utilized when updating the Ra Table. The Ra table will not update when discharge is below this discharge rate. Default is set to 10 which corresponds to C/10.

    2) ResRelax Time - minimum time before resistance updates occur after the beginning of discharge. Default is set to 500 s.

    3) Design Resistance - limits the maximum amount of change allowed in grid-point resistance update during a discharge. Set to the Ra4 grid point value. This value is updated by the gauge when the learning/optimization cycle is run.

    4) Cell Max IR Correct - maximum value of IR correction that will be used to eliminate the effect of IR drop across cell impedance to obtain true OCV if current is flowing during the voltage measurement that is utilized for finding the initial DOD. Default is 400 mV.

    5) Max Res Factor - maximum percentage (ratio) an impedance value stored in the Ra table is allowed to change in a single update in the positive direction. The default in this gauge has been increased to 50 to allow for use as a Host-Side Gauge where batteries may be removable. This larger range is to accommodate removable batteries which may vary slightly. If batteries will be replaced, please take care to still use the same chemistry and similar original design capacity of the replacement cell to ensure that other cell parameters are still valid. If you will not be using replaceable batteries, the default value of Max Res Factor may be reduced to 15.

    6) Min Res Factor - maximum percentage (ratio) an impedance value stored in the Ra table is allowed to change in a single update in the negative direction. The recommended value for min res factor is 1 for when batteries are replaceable, and 3 for non-removable batteries.

    For more information on the recommended settings for replaceable and non-replaceable battery systems, please refer to tables 28 and 28 in Section 8.2.4 of the Datasheet (p. 52) found here: www.ti.com/.../bq34z100-g1.pdf

    Sincerely,
    Bryan Kahler
  • 0 in reply to Bryan Kahler
    Expert 1232 points
    Bryan,

    Thank you for the quick response. I am scaling for both current and capacity. Presently I am having some issues with getting OCV readings and I am verifying my setup before I submit data to you for evaluation, if necessary.